1. Field of the Invention
The present invention relates to a multiplication device for performing multiplication on a multiplicand and plural fixed coefficients and for subsequently outputting the product obtained for a selected one of the fixed coefficients, and also to a fixed coefficient type finite impulse response (FIR) digital filter having a plurality of such multipliers.
2. Description of the Related Art
A multiplication device used in a fixed coefficient FIR digital filter is well known which performs multiplication on a multiplicand and plural fixed coefficients find then outputs the result (product) obtained for a selected one of the fixed coefficients.
FIG. 11 shows the prior art multiplication device 500 for multiplying a common multiplicand X by two fixed coefficients C1 and C2 and then outputting one of the two results, that is, the result obtained for a selected one of the coefficients. As shown in FIG. 11, this multiplication device 500 has two multipliers 50 and 51. One multiplier 50 multiplies the multiplicand X by a fixed coefficient C1 and outputs the result to a selector 52. The other multiplier 51 multiplies the multiplicand X by another fixed coefficient C2 and likewise outputs the result to the selector 52. The selector 52 selects one of the multipliers 50 and 51 based on a selection control signal, which is set according to the fixed coefficient to be used, and passes the result from the selected multiplier 50 or 51 as the product of the multiplication.
The prior art multiplication device 500 as thus described requires the same number of multipliers as the fixed coefficients to be dealt with thereby. An obvious problem with this configuration is that the size of the multiplication device necessarily increases as the number of fixed coefficients increases.